You need to translate the sentence as a whole. The 'frazionabili' refers to the mortgage loans. The division of the housing project (i.e. allocation to the individual members/owners) happens at a second phase, after building is completed, so that the mortgage is first granted to the coop and then later transferred (accollato) to individual members once they become owners.

The Italian national pensions institute (INPS) describes the coops in question as: "cooperative edilizie per la costruzione di case economiche e popolari da assegnare in proprietà ai soci": so title is to be transferred to the members at the time of building, but has not yet been transferred.

The splitting up of the mortgage creates a whole series of potential problems covered by this article: http://elibrary.fondazionenotariato.it/articolo.asp?art=23/2...

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Note added at 1 day 5 hrs (2019-11-03 16:39:39 GMT)
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If you want to make it even more evident that the loans are divisible you could change the syntax: "divisible mortgage loans to housing cooperatives".